During life they were probably covered with horn increasing the length by six inches or perhaps a foot.

The ball-like condyle for articulation of the neck lies far underneath, at the base of the frill, almost in the middle of the skull.
[Illustration: Fig.

39 .-- Skull of _Monoclonius_, a horned dinosaur from the Cretacic (Belly River formation) of Alberta.
One-fifteenth natural size.

The horns over the eyes are rudimentary, and the nasal horn large, reversing the proportions in _Triceratops_.] _Monoclonius, Ceratops, etc._ The _Triceratops_ and another equally gigantic Horned Dinosaur, _Torosaurus_, were the last survivors of their race.

In somewhat older formations of Cretacic age are found remains of smaller kinds, some of them ancestors of these latest survivors, others collaterally related.